diff --git a/problems/0042.接雨水.md b/problems/0042.接雨水.md
index b232ce22..e331967f 100644
--- a/problems/0042.接雨水.md
+++ b/problems/0042.接雨水.md
@@ -640,8 +640,44 @@ func min(a,b int)int{
 }
 ```
 
+单调栈解法
+```go
+func trap(height []int) int {
+   if len(height) <= 2 {
+      return 0
+   }
+   st := make([]int, 1, len(height)) // 切片模拟单调栈，st存储的是高度数组下标
+   var res int
+   for i := 1; i < len(height); i++ {
+      if height[i] < height[st[len(st)-1]] {
+         st = append(st, i)
+      } else if height[i] == height[st[len(st)-1]] {
+         st = st[:len(st)-1] // 比较的新元素和栈顶的元素相等，去掉栈中的，入栈新元素下标
+         st = append(st, i)
+      } else {
+         for len(st) != 0 && height[i] > height[st[len(st)-1]] {
+            top := st[len(st)-1]
+            st = st[:len(st)-1]
+            if len(st) != 0 {
+               tmp := (min(height[i], height[st[len(st)-1]]) - height[top]) * (i - st[len(st)-1] - 1)
+               res += tmp
+            }
+         }
+         st = append(st, i)
+      }
+   }
+   return res
+}
 
 
+func min(x, y int) int {
+   if x >= y {
+      return y
+   }
+   return x
+}
+```
+
 ### JavaScript:
 
 ```javascript